Receiver circuit arrangements or receivers, are used in integrated circuits in a multiplicity of applications. By way of example, a receiver circuit arrangement is provided as an input receiver on an integrated circuit in order, by way of example, to receive data from another integrated circuit. A receiver circuit arrangement of this type is connected to an input signal line for receiving a respective input signal and to an output signal line for outputting a respective output signal. By way of example, inverter circuits connected between an input signal line and output signal line are used as receiver circuit arrangements. An inverter circuit is advantageous primarily with regard to its low current consumption and high switching speeds attainable, but has the disadvantage of a comparatively high sensitivity to input signal fluctuations. A further known embodiment of a receiver circuit arrangement is a differential amplifier circuit, which has often been used as a “chip receiver” heretofore.
A differential amplifier circuit essentially comprises two input transistors, a load element and a current source. The two input transistors connected in parallel are driven by an input voltage and by a reference voltage, respectively. In this case, the input voltage is compared with a predetermined reference voltage and, depending on whether the input voltage lies above or below the reference voltage, the signal state “1” or “0” is supplied at the output of the differential amplifier. Signal transitions from the state “0” to the state “1” are generated by the input voltage being raised from a low voltage value to a high voltage value; in the event of a signal transition from the state “1” to the state “0”, the input voltage of the differential amplifier is lowered from a high voltage level to a low voltage level. As soon as the signal level of the input signal reaches the value of the reference voltage, the signal of the differential amplifier changes from one state to the other.
What is problematic in this case is that the value of the reference voltage usually cannot be held at a fixedly predetermined, nominal value, but rather is subject to fluctuations, for example, on account of technological influences or temperature-dictated influences. Fluctuations in the reference voltage bring about a shift in the operating point of the circuit. This disadvantageously leads to a shift in the point of intersection at which the level of the input voltage intersects the level of the reference voltage. A further consequence is also longer or shorter switching times of the differential amplifier on account of an altered switching behavior of the switching transistors and of the current source transistor, so that the matching or synchronization of a clock signal and an input signal deteriorates.
On account of the trend toward ever smaller supply voltages of an integrated circuit, in the context of the problem area of the shift in the operating point of a differential amplifier, the problem arises that the permissible fluctuation range of the reference voltage decreases further, so that the circuit can be moved from its operating point more easily. Consequently, small deviations of the reference voltage may lead to large deviations of the “duty cycle”, which denotes the ratio of the time period of, in particular, of a high signal level of a signal to the period duration of the respective signal.